Why are my mail pdf attachments showing up as either Dropbox or Evernote icon?

When I receive pdf attachments in Mail, it shows up as either an EverNote or DropBox icon. It used to have a PDF icon that I would click on and Preview would open up and I could view the document or choose to send a copy to another app like Evernote or Dropbox. This started happening on both my iPhone and iPad running 9.3.1. Does anyone have an idea what's causing this?